Detection and classification of oxidative damaging stresses using recombinant bioluminescent bacteria harboring sodA∷, pqi∷, and katG∷luxCDABE fusions

We need to plan streamlined environmental impact assessment for the future X-Press Pearl disasters

The X-Press Pearl disaster illustrates the urgent needs for streamlined environmental impact assessment to inform decision making. The environmental contamination caused by the disaster is complex, and the biological impact of different environmental stressors, and at different biological scales, needs to be determined. Traditional methods for analyzing complex environmental stressors are often inefficient and do not reflect the biological impact of pollution. The combination of chemical stressors and biological impacts is the key to environmental impact assessment based on integrated monitoring. Whole-cell bioreporters are tools for rapid, efficient and quantitative detection of the bioavailability, stressor effects, and toxicity of pollutants, i.e., spanning a wide range of applications. Here we propose the view that using whole-cell bioreporter technology to streamline short-term environmental impact assessment for maritime disasters such as the X-Press Pearl is more fit-for-purpose/practical than other approaches in use.

Sensing of plant hydrolysate-related phenolics with an aaeXAB::luxCDABE bioreporter strain of Escherichia coli

A bioluminescent Escherichia coli bioreporter strain to detect hydrolysate related phenolics was developed by cloning the aaeXAB promoter from E. coli upstream of the luxCDABE genes. E. coli str. DH5α carrying this plasmid (pDMA3) was responsive to sub-inhibitory concentrations of plant hydrolysate-related phenolics, such as ferulic and vanillic acids, responding to these compounds at concentrations as low as 9.8 and 4.9 mg/L, respectively. Experiments with a mixture of the compounds showed similar responses as with single compound tests, with a minimum detectable concentration of 19.5mg/L. Finally, tests using rice straw hydrolysates were conducted, with E. coli str. DH5α/pDMA3 showing a maximum induction of 33-fold and a minimum detectable phenolic concentration of 9.3mg/L, based upon Folin-Ciocalteu's reagent. These results demonstrate that this bioreporter maintains its sensitivity even with hydrolysate samples and that it can be potentially applied within biofuel industries to detect phenolics present within plant hydrolysates.

Sub-toxic effects of CuO nanoparticles on bacteria: kinetics, role of Cu ions and possible mechanisms of action

The sub-toxic effects of CuO nanoparticles (nano-CuO) were evaluated using three recombinant luminescent Escherichia coli bacteria responding specifically to (i) reactive oxygen species (ROS), (ii) single-stranded DNA breaks and (iii) bioavailable Cu ions. Using these sensors we showed that nano-CuO induces the formation of superoxide anions, hydrogen peroxide and single-stranded DNA already at very low sub-toxic levels (0.1 mg Cu/L). The maximal sub-toxic response of all biosensors to nominal concentrations of nano-CuO, micro-CuO (size control) and CuSO(4) (solubility control) occurred at ~6, ~600 and ~0.6 mg Cu/L, respectively. According to the chemical analysis all the latter concentrations yielded ~0.6 mg of soluble Cu/L, indicating that dissolution of CuO particles was the key factor triggering the ROS and DNA damage responses in bacteria. Cu-ions chelation studies also showed that CuO particles were not involved in these stress responses. The solubilization results were confirmed by Pseudomonas fluorescens Cu-ion sensor.

A microfluidic concentrator array for quantitative predation assays of predatory microbes

We present a microfabricated concentrator array device that makes it possible to quantify the predation rate of Bdellovibrio bacteriovorus, a predatory microbe, toward its prey, Escherichia coli str. MG1655. The device can accumulate both prey and predator microbes sequentially within a series of concentrator arrays using the motility of the microbes and microfabricated arrowhead-shaped ratchet structures. Since the device can constrain both prey and predator cells within 200 pL chambers at a desired range of cell densities, it was demonstrated that the device cannot only enhance the possibility of studying predation processes/cycles directly at a single cell level but can also quantify the predation rates indirectly by measuring the time-dependent fluorescent intensity signals from the prey. Furthermore, the device can produce a wide range of initial prey to predator density ratios within various concentrator arrays through the use of microfluidic mixer structures on a single array chip, which allows us to study many different conditions with a single set of cultures, and quantitatively characterize the predation behaviour/rate. Lastly, we note that this novel concentrator array device can be a very powerful tool facilitating studies of microbial predations and microbe-microbe interaction and may be broadly used in other microbial biotechnological applications.

Microbial whole-cell arrays

The coming of age of whole‐cell biosensors, combined with the continuing advances in array technologies, has prepared the ground for the next step in the evolution of both disciplines – the whole‐cell array. In the present review, we highlight the state‐of‐the‐art in the different disciplines essential for a functional bacterial array. These include the genetic engineering of the biological components, their immobilization in different polymers, technologies for live cell deposition and patterning on different types of solid surfaces, and cellular viability maintenance. Also reviewed are the types of signals emitted by the reporter cell arrays, some of the transduction methodologies for reading these signals and the mathematical approaches proposed for their analysis. Finally, we review some of the potential applications for bacterial cell arrays, and list the future needs for their maturation: a richer arsenal of high‐performance reporter strains, better methodologies for their incorporation into hardware platforms, design of appropriate detection circuits, the continuing development of dedicated algorithms for multiplex signal analysis and – most importantly – enhanced long‐term maintenance of viability and activity on the fabricated biochips.

Microbial cell arrays

The coming of age of whole-cell biosensors, combined with the continuing advances in array technologies, has prepared the ground for the next step in the evolution of both disciplines - the whole cell array. In the present chapter, we highlight the state-of-the-art in the different disciplines essential for a functional bacterial array. These include the genetic engineering of the biological components, their immobilization in different polymers, technologies for live cell deposition and patterning on different types of solid surfaces, and cellular viability maintenance. Also reviewed are the types of signals emitted by the reporter cell arrays, some of the transduction methodologies for reading these signals, and the mathematical approaches proposed for their analysis. Finally, we review some of the potential applications for bacterial cell arrays, and list the future needs for their maturation: a richer arsenal of high-performance reporter strains, better methodologies for their incorporation into hardware platforms, design of appropriate detection circuits, the continuing development of dedicated algorithms for multiplex signal analysis, and - most importantly - enhanced long term maintenance of viability and activity on the fabricated biochips.

Prediction and classification of the modes of genotoxic actions using bacterial biosensors specific for DNA damages

We report on a novel approach to predict the mode of genotoxic action of chemicals using a series of DNA damage specific bioluminescent bacteria. For this, a group of seven different DNA damage sensing recombinant bioluminescent strains were employed. Each of these strains was tested against model DNA damaging agents, such as mitomycin C (MMC), 1-methyl-1-nitroso-N-methylguanidine (MNNG), nalidixic acid (Nal) and 4-nitroquinoline N-oxide (4-NQO). These biosensors were grouped based on their responses to a specific mode of genotoxic action, such as (a) DNA damage cascade response (biosensor with nrdA-, dinI- and sbmC-lux), (b) SOS response or DNA repair (strains carrying recA-, recN- and sulA-lux), and (c) DNA damage potentially by alkylation (biosensor with alkA-lux). The differential response patterns and its strength of these strains to various model genotoxicants allowed classifying the chemical's potential genotoxic mode. Therefore, it is possible to elucidate and classify the mode of genotoxic impacts of an unknown sample and that together they may be utilized in the pre-screening steps of new drugs, newly synthesized chemicals, food and environmental contaminants.